‘All substances are poisons … dose differentiates a poison.'
---Paracelsus (1493-1541)
HEAVY METALS
Toxic heavy metals can cause the following health problems:
CADMIUM
· Renal dysfunction
· Obstructive lung diseases and has been linked to lung cancer.
· Bone defects in humans and animals.
CHROMIUM
· Ulceration
· Kidney and liver damage
· Damage to circulatory and nerve tissues.
COPPER
· Anemia, liver and kidney damage, and stomach and intestinal irritation
LEAD
· Problem in the synthesis of hemoglobin
· Damage to the kidneys, gastrointestinal tract, joints, reproductive system and the nervous system
MERCURY
· Tremors, gingivitis and/or minor psychological changes
· Damage to the brain and the central nervous system
· Congenital malformation
NICKEL
· Decreased body weight, heart and liver damage
· Skin irritation
ARSENIC
· Kidney and liver damage
· Death
ALUMINUM
· Bone disorders including fractures, osteopenia and osteomalacia
HEAVY METALS TESTING
ZINC PROTOPORPHYRIN (ZPP) TEST
· This is usually done to test for chronic lead exposure.
· The test result will increase if positive for lead exposure since lead interferes with RBCs ability to make hemoglobin.
· ZPP reflects an average of lead exposure but not recent exposure.
· The result is normal until the lead concentration is greater than 25 micrograms per deciliter.
· ZPP is not sensitive enough because values do not rise until lead concentrations exceed the acceptable range.
ATOMIC ABSORPTION SPECTROMETRY (AAS)
· It is the most widely used instrument for clinical trace element analysis in biological samples.
GRAPHITE FURNACE AAS (GFAAS)
· It has improved the limit of quantitation (LOQ) to parts per billion (ppb, μg/L) and permits the simultaneous measurement of multiple elements.
· Zeeman Effect background correction improves the element signal measurement when testing in complex specimens such as serum, plasma or blood, and other specimen-handling enhancements have further improved sensitivity and precision.
FLAME AAS (FAAS) has a LOQ of parts per million (ppm, mg/L).
ATOMIC EMISSION SPECTROMETRY (AES)
· Consists of flame AES and plasma source emission spectrometry, which measures photon output rather than photon absorption as in AAS. The emission line(s) of the excited electrons are measured. The LOQ is ppm (mg/L). The sample in neutron activation analysis (NAA) is irradiated with low-energy neutrons for the production of radioactive nuclides. In NAA there is excitation of the atomic nucleus, so that the trace element is determined independently of its physical or chemical state. The newly formed radionuclide emits X- or γ-rays. The LOQ is ppb (μg/L) to parts per trillion (ppt, ng/L) with multi-element detection, but with a limited dynamic range. This technique is especially suited for in vitro trace element determination in biologic matrices. In instrumental neutron activation analysis (INAA) there is direct measurement of the emitted X or γ radiation. Inductively coupled plasma–mass spectroscopy (ICP-MS) is a highly sensitive and specific method for the measurement of multiple trace elements in a single run over an especially broad dynamic range with low background interference and LOQs of ppb (μg/L) to ppt (ng/L). An internal standard is used for enhanced precision ( Milne, 1994 ; Chan, 1998a ).
· The first morning void urine is less affected by recent dietary intake.
· May be obtained from accessible tissues (hair, nails) and body fluids (serum, urine), or the activity of a trace element-dependent enzyme. Hair, fingernail or toenail analyses provide a retrospective window or an assessment of chronic exposure for the period of hair or nail growth ( Gibson, 2002 ).
Table 26-5 -- Properties of Essential Trace Mineral Elements
| Element | Tissue distribution | Body content | Transport (Reference value) | Excretion | ||||||||||||
| Chromium | Spleen, heart | 4–6 mg Cr (III) | Transferrin-P 0.15 μg/mL Cr (0.12–2.1 μg/L) | Urine 100–200 ng/day | ||||||||||||
| Cobalt | Muscle, liver, fat | 1.1 mg | Albumin (0.11–0.45 μg/L) | Urine 80% | ||||||||||||
| Copper | Muscle and liver |
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| Liver 30–50 μg/g dry; 50–70% of body Cu | 50–80 mg (1.2–2.5 μg/g fat-free tissue) | Ceruloplasmin 60–95%, albumin, transcuperin (Cu-S: 70–140 μg/dL AAS) | Feces includes bile and unabsorbed dietary Cu | ||||||||||||
| Iodine | Thyroid: 70–80% of total body I in thyroxin bound to thyroglobulin | 15–20 mg (11–15 mg in thyroid) | Thyroxine-binding protein, 80% thyroxine-binding prealbumin (transthyretin) | Urine 100–150 μg/day | ||||||||||||
| Iron | RBC Hb 400–600 mg/L, liver, spleen, bone marrow 25%, myoglobin |
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| Bile 84 μg/kg, blood loss, menses, GI mucosal cells | ||||||||||||
| Manganese | Liver, bone, pancreas | 12–20 mg |
| Bile and intestinal secretions | ||||||||||||
| Molybdenum | Liver, kidney, bone, adrenal | Blood 30–700 nmol/L | RBC protein, α1-macroglobulin (S: 8–34 μg/L) | Urine 90%, bile 10% | ||||||||||||
| Selenium | Liver, kidney, muscle | 15 mg | Protein [Se-P: 7–30 μg/dL] | Urine 60%, feces 40% | ||||||||||||
| Zinc | Muscle 60%, bone 30%, liver, prostate, semen | 1.2–2.3 g | Albumin 60–70%, α2-macroglobulin (Zn-P: 11–22 μmol/L) | Feces, gut secretions, GI mucosal cells |
Data from: Fausto da Silva, 1991 ; Milne, 1994 ; O'Dell, 1997 ; Kohlmeier 2003 .
| P = plasma; S = serum; AAS = atomic absorption spectrometry. |
Source: Henry’s Clinical Diagnosis and Management by Laboratory Methods 21st Edition, Edited By Richard A. McPherson, Matthew R. Pincus, 2007
